the best way to do it is to adjust your timer(if you don't have one go and get it) to 12 hours on 12 hours off in a time that is good for ya.don't forget to keep us posted with the flowering dude . good luck! Cheers!!! CheetaHive been running my CFL's on my ladies 24/0 throughout veg. i want to switch to 12/12 tommorow, and im wondering the best way to do it. DO i need to give it 16 hours of straight dark then change it? i want to have the lights on from 7pm to 7am